The invention relates generally to precision loading systems for loading coal or other particulate material into a moving train of railcars and, more particularly, to multiple-batch loading systems and methods which are capable of accommodating railcars of a wide range of capacities and designs.
For economic reasons, it is desirable to accurately load railcars to target weights very near the respective maximum weight capacities of the individual cars. Overloading a railcar is undesirable because equipment damage can result. Underloading is undesirable because railcar capacity is not efficiently utilized.
The capacities and designs of railcars vary greatly, from country to country, as well as within the same country. In the United States, the capacity of a typical railcar is 120 tons (109 metric tons) of coal. However, railcars of much greater capacity are also employed. Thus, at least in the United States, articulated railcars having coal-carrying capacities of up to 500 tons (454 metric tons) are employed. In some other countries, relatively small railcars having capacities ranging from 60 tons (54 metric tons) to 90 tons (82 metric tons) are employed.
As is for example disclosed in Campbell et al U.S. Pat. No. 4,629,392, what may be characterized as a single-batch loading system for loading railroad cars with coal includes a relatively larger surge bin positioned above a relatively smaller weigh bin. Below the surge bin is a controlled charging gate for charging batches of coal from the surge bin into the weigh bin. The weigh bin is mechanically supported on load cells, such that the weight of the weigh bin and coal contained therein can be determined. Below the weigh bin is a controlled discharge gate for discharging coal from the weigh bin through a loading chute into the railroad cars as they travel past below. The surge bin is supplied by a conveyor system which runs substantially continuously while the train is traveling below past the train loading system, at a conveyor rate consistent with the average loading rate as successive railroad cars of the moving train, traveling for example at a speed of one-half mile per hour to one mile per hour (0.8 km/hr to 1.6 km/hr), are loaded.
During operation of such a coal train loading system, the charging gate is opened to charge from the surge bin into the weigh bin a batch of coal having a weight equal to the target weight of coal to be loaded into an individual railroad car, thereby making up a weighed batch of coal. Then, as the railroad car reaches its proper position below the weigh bin and loading chute, the discharge gate is opened, commencing the discharge of the weighed batch of coal from the weigh bin into the railroad car. Ideally, coal flows continuously into the railroad car, filling each railroad car evenly from front to back. Such a single-batch train loading system becomes impractical with relatively larger-capacity railcars.
Thus, for economic reasons, as well as for practical reasons when relatively larger-capacity railcars are to be loaded, it is desirable to employ multiple-batch systems and methods which achieve acceptably high loading rates with smaller, and therefore less costly, facilities. Two-batch, three-batch and four-batch railcar loading systems are known. For example, a three-batch system is disclosed in Walker U.S. Pat. No. 6,155,767.